Science · Grade 5 · Internal Systems of Living Things · Term 2

Cells: The Building Blocks of Life

Students will learn about the basic structure and function of plant and animal cells.

• Ontario Curriculum Expectations
• 4-LS1-1

About This Topic

The digestive and excretory systems are the focus of this life systems unit, where students learn how the body fuels itself and manages waste. They trace the journey of food from the mouth through the stomach and intestines, learning how mechanical and chemical digestion break down nutrients for absorption. The Ontario curriculum emphasizes the interconnectedness of these organs and how they work together to maintain the body's internal balance, or homeostasis.

Students also explore the excretory system, specifically the role of the kidneys and bladder in filtering blood and removing liquid waste. This topic is an excellent entry point for discussing healthy living and the impact of diet on body systems. It also allows for a respectful inclusion of Indigenous perspectives on traditional diets and the medicinal use of local plants to support digestive health.

This topic comes alive when students can create physical models of the digestive tract to visualize the scale and function of each organ.

Key Questions

1. Compare the key differences between plant and animal cells.
2. Explain how different cell parts contribute to the cell's overall function.
3. Construct a model of a cell, labeling its essential components.

Learning Objectives

• Compare and contrast the primary organelles found in typical plant and animal cells.
• Explain the function of at least three key organelles within a cell, relating their role to the cell's overall survival.
• Construct a labeled 3D model of either a plant or animal cell, accurately representing the size and location of major components.
• Identify the essential components common to both plant and animal cells, such as the nucleus and cytoplasm.

Before You Start

Characteristics of Living Things

Why: Students need to understand what defines life to appreciate that cells are the fundamental units of living organisms.

Introduction to Organisms

Why: Students should have a basic understanding of different types of organisms (plants and animals) before comparing their cellular structures.

Key Vocabulary

Cell	The basic structural, functional, and biological unit of all known organisms. It is the smallest unit of life.
Organelle	A specialized subunit within a cell that has a specific function, such as the nucleus or mitochondria.
Nucleus	The central organelle in eukaryotic cells, containing the cell's genetic material (DNA) and controlling its growth and reproduction.
Cytoplasm	The jelly-like substance filling a cell, enclosing the organelles and providing a medium for biochemical reactions.
Cell Wall	A rigid outer layer found in plant cells, providing structural support and protection to the cell.
Chloroplast	An organelle found in plant cells that conducts photosynthesis, converting light energy into chemical energy.

Watch Out for These Misconceptions

Common Misconception

Digestion only happens in the stomach.

What to Teach Instead

Students often think the stomach does all the work. Teachers should emphasize that digestion begins in the mouth and the most important nutrient absorption happens in the small intestine. A 'time-lapse' map of a meal's journey helps students see the stomach is just one stop.

Common Misconception

The excretory system is only about going to the bathroom.

What to Teach Instead

Students often overlook the role of the skin (sweat) and lungs (CO2) in removing waste. Teachers can use a 'waste management' analogy to show how the body has multiple 'exit routes' for different types of cellular waste. Peer discussion about why we sweat during exercise helps surface this.

Active Learning Ideas

Simulation Game: The Digestive Journey

Students use household items to mimic digestion: a bag for the stomach, crackers for food, water for saliva, and a stocking for the small intestine. They physically mash the 'food' and squeeze it through the 'intestine' to see how nutrients are absorbed through the walls while waste moves on.

50 min·Small Groups

Gallery Walk: Organ Infographics

Each group is assigned one organ (e.g., liver, kidneys, large intestine). They create a poster showing its 'job description,' its 'coworkers' (connected organs), and what happens if it 'goes on strike.' The class rotates to learn how each part contributes to the whole system.

40 min·Small Groups

Think-Pair-Share: The Nutrient Path

Ask: 'How does a piece of apple end up in your big toe?' Students work in pairs to trace the path from ingestion to absorption into the bloodstream. This helps them connect the digestive system to the circulatory system, reinforcing the idea of body systems working together.

15 min·Pairs

Real-World Connections

• Biologists at research institutions like the Hospital for Sick Children use advanced microscopy to study cell structures and functions, aiding in the development of new medical treatments for diseases.
• Farmers and agricultural scientists study plant cells, particularly chloroplasts and cell walls, to improve crop yields and develop more resilient plant varieties for food production.
• Medical illustrators create detailed diagrams and models of cells and tissues for textbooks, scientific journals, and patient education materials, helping others visualize complex biological structures.

Assessment Ideas

Quick Check

Provide students with a Venn diagram template. Ask them to fill it in by listing unique features of plant cells on one side, unique features of animal cells on the other, and shared features in the middle. Review as a class.

Discussion Prompt

Pose the question: 'If a cell were a factory, what would be the job of the nucleus? What about the cytoplasm?' Facilitate a class discussion, encouraging students to use cell part names and explain their functions.

Exit Ticket

On a small slip of paper, ask students to draw one organelle (not the nucleus) and write one sentence explaining its job. Collect these as students leave to gauge understanding of specific organelle functions.

Frequently Asked Questions

What is the difference between mechanical and chemical digestion?

Mechanical digestion is the physical breaking down of food into smaller pieces, like chewing with teeth or the stomach churning. Chemical digestion uses substances like enzymes and stomach acid to break those pieces down into even smaller molecules that the body can actually absorb into the blood.

Why is the small intestine so long?

The small intestine is about 6-7 meters long to provide a massive surface area for nutrient absorption. It is lined with tiny finger-like projections called villi that maximize the contact between the digested food and the bloodstream, ensuring the body gets as much energy as possible.

How can active learning help students understand internal body systems?

Internal systems are hard to visualize because they are hidden. Active learning, like building a 'pantyhose intestine' or acting out the path of a nutrient, makes these processes visible and tactile. When students have to physically move 'food' through a system, they better understand the sequence and function of each organ.

How do traditional Indigenous diets support the digestive system?

Traditional diets, often consisting of 'The Three Sisters' (corn, beans, and squash), provide a perfect balance of fiber, protein, and complex carbohydrates that promote healthy digestion. Many Indigenous communities also use plants like ginger or peppermint for their natural ability to soothe the digestive tract, showing a deep historical understanding of body systems.